Washington Nationals third baseman Ryan Zimmerman is a former Gold Glove winner, but his throwing problems have become an issue this season.

Zimmerman committed his fourth throwing error in Tuesday’s loss to the Miami Marlins, and it led to unearned runs crossing the plate. Zimmerman always has been prone to throwing errors, even during his Gold Glove season in 2009. But the errors are piling up early this season.

“I’m working on it. I’m doing everything I can to make those plays and help this team. Unfortunately right now, I’ve made a few errors but I’ll go back out there tomorrow and hope every ball’s hit my way and I’ll go right back at it,” Zimmerman told The Washington Post.

Zimmerman had shoulder surgery this past offseason, but the newspaper notes that might not be the cause of his struggles. After all, he is making many throws without a hitch, even some tough throws on strong defensive plays. It has been the routine throws that have been problematic.

“That’s why it’s so tough, too,” Zimmerman told the newspaper. “Everything feels good. I long toss, my arm feels strong, everything’s good. It’s just a matter of me sticking with it and not mentally getting frustrated, just going out there and knowing that I can do that kind of stuff. I know I can do that.”